My invention relates to a wayside signaling system for controlling cab signals and/or speed control apparatus carried on vehicles traversing a fixed roadway. Specifically, the invention pertains to a fail-safe wayside arrangement by which speed or cab signal commands are transmitted to railroad trains through wire loops load between and parallel to the track rails while retaining all the safety characteristics inherent in the transmission of such commands through the rails.
Although the transmission of speed and cab signal commands through the rails of the railroad track is an inherently failsafe arrangement, due to train rail shunts, it does occasionally create or build-in problems, particularly in electrified rapid transit systems. The use of wire loop arrangements to carry such commands can eliminate many of these problems and disadvantages. Among the advantages of using the loop transmitting system are negligible noise in the transmitted speed commands induced by propulsion current, cab signal sneak paths through bond connections are not as probable, the train apparatus does not have to respond to such a wide range of cab signal intensity or voltage levels, and the complications of physical attachment through some type of track bonds to the rails is eliminated. A principle objection to the use of wire loops obviously is that the signal carried therein is not shunted by the train moving through the stretch. Therefore, a following train could receive the same speed command as the leading train in the same signal block. This problem may be overcome by application of a stop command, indicating a very low speed limit, in the loops in the approach section to an occupied track section and by a preselected arrangement of loops, i. e., their pattern and positioning. A relatively fail-safe pattern for such wire loops is disclosed in the copending patent application, Ser. No. 719,336, having a common assignee and filed the same date as this application by Thomas J. Bourke and Kenneth J. Buzzard for a Transmitting Loop Arrangement for Railroad Cab Signal and Speed Control System.
Accordingly, an object of my invention is a wayside signaling system using wire loops for controlling cab signal or speed control apparatus on vehicles traversing a stretch of fixed roadway.
Another object of this invention is control circuitry for cab signal transmitting loops along a stretch of railroad track which provides fail-safe operation of the speed control apparatus on trains traversing that track.
Still another object of my invention is a train control signaling system for transmitting speed commands from wayside locations to control apparatus on trains traversing a stretch of track, using wire loops positioned in a predetermined pattern parallel to the rails of the stretch.
A further object of the invention is a wayside signaling arrangement for a railroad cab signal and speed control system which establishes traffic direction through a stretch of single track and supplies speed commands to trains traversing that track in accordance with the established traffic direction, with all traffic and speed signals transmitted through wire loops positioned between and parallel to the rails.
It is also an object of my invention to provide wayside control circuits for transmitting cab signal or speed control commands to trains traversing a stretch of single track in either direction, with train detection provided by track circuits but the speed commands transmitted through wire loops laid in a predetermined pattern between the rails, the control circuits being designed to provide positive train stops prior to entering an occupied track section.
A still further object of the invention is a speed control system for trains traversing a stretch of railroad track in either direction in which the speed commands are transmitted through wire loops laid betweeen the rails for inductive pickup by train carried apparatus, the loops being positioned in a predetermined pattern and supplied with control commands in a manner to provide fail-safe operation of the trains in response to advanced traffic conditions along the stretch of track.
Other objects, features, and advantages of the invention will become apparent from the following specification and appended claims when taken in connection with the accompanying drawings.